The present invention relates to a defect testing apparatus and a defect testing method for inspecting a state of generation of defects such as foreign particles in a fabrication process such as a semiconductor fabrication process, a liquid-crystal-display fabrication process and a print-board fabrication process wherein a defect such as a foreign particle generated in a process to create a pattern on a substrate to produce an object is defected and analyzed in order to determine a countermeasure.
In the conventional semiconductor fabrication method, a foreign particle existing on a semiconductor substrate also known as a wafer causes a defect such as poor insulation of a wire or a short circuit. Furthermore, in the case of a miniaturized semiconductor device, an infinitesimal foreign particle existing in a semiconductor substrate results in poor insulation of a capacitor or destruction of typically a gate oxide film. These foreign particles are introduced to get mixed with a semiconductor material in a variety of states due to a variety of causes. For example, a foreign particle is generated by a movable part of a transportation apparatus or a human body. A foreign particle can also be generated as a result of a chemical reaction in processing equipment using a process gas or mixed with chemicals or a raw material.
Likewise, if a foreign particle is introduced to get mixed with a pattern, causing some defects in a process to fabricate a liquid-crystal display device, the resulting display device is not usable. The process to fabricate a print board is in the same situation. That is to say, a mixed foreign particle causes a poor connection and a short circuit in a pattern.
Prior arts related to apparatuses and methods for detecting defects such as foreign particles are disclosed in Japanese Patent Laid-open No. Hei 1-250847, Japanese Patent Laid-open No. Hei 6-258239, Japanese Patent Laid-open No. Hei 6-324003, Japanese Patent Laid-open No. Hei 8-210989 and Japanese Patent Laid-open No. Hei 8-271437 and referred to as prior arts 1, 2, 3, 4 and 5 respectively.
In prior art 1, there is described an inspection apparatus for inspecting surface characteristics of a substrate. The inspection apparatus includes a storage means for storing desired surface characteristics of the substrate, a radiation means for radiating a beam to an area on the surface of the substrate to be inspected all but uniformly, a TDI image sensor means for forming an image of the area on the surface of the substrate to which the beam is radiated by the radiation means, and a comparison means for comparing the image of the area on the surface of the substrate formed by the TDI image sensor means with the desired surface characteristics of the substrate stored in the storage means.
In prior art 2, there is described a defect inspecting apparatus comprising a conveyance means for conveying a substrate having repetitive patterns with different pitches, a radiation means for forming a plane-wave beam into a straight line and radiating the plane-wave beam to the substrate, a space filter, a detector for detecting an optical image formed by an image formation optical system and supplied to the detector through the space filter, elimination means for comparing signals, which are generated to represent the repetitive patterns with large pitches on the substrate and supplied to the elimination means through the space filter for an elimination purpose, with each other, and a defect detection means for detecting a defect caused by typically a very small extraneous material existing on the substrate on the basis of a signal generated by the elimination means.
In prior art 3, there is described a defect inspecting apparatus comprising a detection head, a pitch detection means, an operator processing system, an extraneous-material data memory, a large-extraneous-material data memory, a pattern memory, a software processing system, a parameter transfer means, an extraneous-material memory, a coordinate-data creation means and a microcomputer wherein the detection head includes a radiation means, a detection optical system, a space-filter unit, a detector, an operational amplifier and an A/D converter.
In prior art 4, there is described a very-small-defect detecting apparatus for detecting a very small defect caused by typically a very small extraneous material having a size in a range of 0.3 xcexcm to 0.8 xcexcm or smaller and existing on a substrate by splitting a laser beam emitted from a semiconductor laser oscillator into a plurality of optical beams not interfering each other so as to make intensities of beams reflected by a thin film created on the substrate smooth or uniform, converging the optical beams and radiating the converged optical beams at effectively the same time to the thin film passing the beams at different incidence angles T1 to Tn, converging lights scattered by a very small defect by using a light converging lens, and detecting the converged lights by using a detector such as a TDI image sensor.
In prior art 5, there is described an extraneous-material inspecting apparatus comprising a radiation optical system for radiating a beam generated by a light source to a sample comprising repetitive chips, a detection optical system including a linear image sensor for receiving lights reflected and scattered by the sample and for converting the reflected and scattered lights into a signal, and an interchip comparison means for comparing signals output by the linear image sensor employed in the detection optical system for the repetitive chips in order to detect a comparison mismatch as existence of an extraneous material on the sample, wherein the radiation optical system includes, a shading correction plate having a plurality of curved transmission portions created thereon for an intensity distribution of the beam generated by the light source to correct the beam radiation so as to give an all but equal phase distribution in the straight-line transversal direction and an all but uniform radiation intensity in the straight-line longitudinal direction, and a light converging subsystem for converging the radiated beam and radiating the converged beam to the sample in a slanting direction with respect to the surface of the sample.
In the prior arts described above, however, it is not easy to detect a defect cause by a very small extraneous material with a size of about 0.1 xcexcm or smaller existing on a substrate, on which repetitive patterns coexist with non-repetitive patterns, with a high degree of sensitivity and at a high speed.
This is because, with the prior arts described above, the farther the distance from a location in an inspected area to the optical axis of the detection optical system, the lower the MTF (Modulation Transfer Function) for the location so that the illumination intensity of the radiated light in regions surrounding the inspected area is not sufficient, making it difficult to inspect a defect with a high degree of sensitivity and at a high speed.
It is thus an object of the present invention addressing the problems described above to provide a defect inspecting apparatus and a defect inspection method that are capable of inspecting an area of inspection also for a defect caused by typically a very small extraneous material having a size of about 0.1 xcexcm or smaller with a high degree of sensitivity and at a high speed by effectively utilizing the light quantity of a Gaussian optical beam emitted by an ordinary low-cost light source.
It is another object of the present invention to provide a defect inspecting apparatus and a defect inspection method that are capable of inspecting an area of inspection also for a defect caused by typically a very small extraneous material having a size of about 0.1 xcexcm or smaller by employing a TDI image sensor for receiving an optical image based on a DUV (Deep Ultra Violet) laser beam obtained from a substrate being inspected.
It is a further object of the present invention to provide a defect inspecting apparatus and a defect inspection method that are capable of inspecting an area of inspection also for a defect caused by typically a very small extraneous material having a size of about 0.1 xcexcm or smaller with a high degree of sensitivity and at a high speed by effectively utilizing the light quantity of a beam emitted by a lamp serving as a light source and by solving the problem of an insufficient illumination intensity in regions surrounding an area of detection on a substrate serving as an object of inspection with the insufficient illumination intensity caused by the fact that, the farther the distance from a region to the optical axis of the detection optical system, the lower the MTF for the region.
It is a still further object of the present invention to provide a defect inspecting apparatus and a defect inspection method that are capable of inspecting an area of inspection also for a defect caused by typically a very small extraneous material having a size of about 0.1 xcexcm or smaller with a high degree of sensitivity and at a high speed by effectively utilizing the light quantity of a Gaussian optical beam emitted by an ordinary low-cost light source and by solving the problem of an insufficient illumination intensity in regions surrounding an area of detection on a substrate serving as an object of inspection with the insufficient illumination intensity caused by the fact that, the farther the distance from a region to the optical axis of the detection optical system, the lower the MTF for the region.
In order to achieve the objects described above, the present invention is characterized in that, in an area with a minimum illumination intensity in an illumination-intensity distribution within a radiation range, radiation of a beam is implemented to give a maximum illumination intensity and the S/N ratio of a signal representing a detected beam is maximized in order to improve the detection sensitivity and to increase the throughput.
That is to say, the present invention is characterized in that, by radiating a Gaussian optical beam to an area of detection on a substrate serving as an object of inspection with the Gaussian optical beam shaped to provide a maximum illumination intensity on the outermost circumference (or the periphery) of the area of detection, the sensitivity (the S/N ratio) on the outermost circumference in a detector can be increased and a defect caused by typically a very small extraneous material existing in the area of detection can be detected with a high degree of sensitivity and at a high speed. It should be noted that, by a maximum illumination intensity, an illumination intensity of about 60% of the illumination intensity at the center of the area of detection is meant.
In addition, the present invention also provides a defect inspection method and an apparatus adopting the method comprising the steps of:
using a radiation optical system including a radiation light source to radiate a Gaussian light beam to an area of detection on a substrate serving as an object of inspection and having a circuit pattern created thereon wherein the Gaussian light beam is shaped to give an illumination-intensity distribution of a Gaussian distribution having a standard deviation about equal to the distance from the optical axis of the area of detection to the periphery of the area of detection;
using a detection optical system to form an optical image of the area of detection on the substrate serving as an object of inspection by radiation of the shaped Gaussian light beam to a photo-sensitive surface of a detector corresponding to the area of detection;
detecting a picture signal corresponding to the area of detection and originating from the detector; and
detecting a defect caused by typically an extraneous material existing in the area of detection on the basis of the detected picture signal.
Furthermore, the present invention also provides a defect inspection method and an apparatus adopting the method comprising the steps of:
using a radiation optical system to radiate a Gaussian light beam to an area of detection on a substrate serving as an object of inspection and having a circuit pattern created thereon wherein the Gaussian light beam is shaped by adaptation of the diameter or the longitudinal length of the beam to the distance between peripheries having the optical axis of the area of detection as the center thereof so that the ratio of the illumination intensity on the peripheries of the area of detection to the illumination intensity at the center of the area of detection is in a range of about 0.46 to about 0.73 or, ideally, in a range of about 0.54 to about 0.67;
using a detection optical system to form an optical image of the area of detection on the substrate serving as an object of inspection by radiation of the shaped Gaussian light beam to a photo-sensitive surface of a detector corresponding to the area of detection;
detecting a picture signal corresponding to the area of detection and originating from the detector; and
detecting a defect caused by typically an extraneous material existing in the area of detection on the basis of the detected picture signal.
Moreover, in the defect inspection method and the apparatus adopting the method provided by the present invention, the Gaussian light beam has a slit shape and the substrate serving as an object of inspection is moved relatively to the Gaussian light beam with a slit shape in a direction crossing the longitudinal direction of the Gaussian light beam.
Further, in the defect inspection method and the apparatus adopting the method provided by the present invention, the detector is a TDI image sensor.
In addition, in the defect inspection method and the apparatus adopting the method provided by the present invention, the shaped Gaussian light beam is radiated to the area of radiation on the substrate serving as an object of inspection in a slanting direction with respect to the surface of the area.
Furthermore, the present invention also provides a defect inspection method and an apparatus adopting the method comprising the steps of:
using a radiation optical system to radiate a Gaussian light beam to an area of detection on a substrate serving as an object of inspection and having a circuit pattern created thereon wherein the Gaussian light beam is shaped wherein the Gaussian light beam is shaped by adaptation of the diameter or the longitudinal length of the beam to the distance between peripheries having the optical axis of the area of detection as the center thereof so that the ratio of the illumination intensity on the peripheries of the area of detection to the illumination intensity at the center of the area of detection is in a range of about 0.46 to about 0.73 or, ideally, in a range of about 0.54 to about 0.67;
using a detection optical system to form an optical image of the area of detection on the substrate serving as an object of inspection by radiation of the shaped Gaussian light beam to a photo-sensitive surface of a detector corresponding to the area of detection;
detecting a picture signal corresponding to the area of detection and originating from the detector; and
detecting a defect caused by typically an extraneous material existing in the area of detection on the basis of the detected picture signal.
Moreover, the present invention also provides a defect inspection method and an apparatus adopting the method comprising the steps of:
using a radiation optical system to radiate a DUV beam to an area of detection on a substrate serving as an object of inspection and having a circuit pattern created thereon;
using a detection optical system to form an optical image of the area of detection on the substrate serving as an object of inspection by radiation of the shaped DUV beam on a DUV-light-sensitive surface of a TDI image sensor corresponding to the area of detection;
detecting a picture signal corresponding to the area of detection and originating from the TDI image sensor; and
detecting a defect caused by typically an extraneous material existing in the area of detection on the basis of the detected picture signal.
Further, the present invention also provides a defect inspection method and an apparatus adopting the method comprising the steps of:
using a radiation optical system to radiate a DUV beam to an area of detection on a substrate serving as an object of inspection and having a circuit pattern created thereon wherein the DUV beam is shaped to give an illumination-intensity distribution of a Gaussian distribution having a standard deviation about equal to the distance from the optical axis of the area of detection to the periphery of the area of detection;
using a detection optical system to form an optical image of the area of detection on the substrate serving as an object of inspection by radiation of the shaped DUV beam on a DUV-light-sensitive surface of a TDI image sensor corresponding to the area of detection;
detecting a picture signal corresponding to the area of detection and originating from the TDI image sensor; and
detecting a defect caused by typically an extraneous material existing in the area of detection on the basis of the detected picture signal.
According to a configuration described above, a problem of an insufficient illumination intensity on the periphery of an area of detection on a substrate serving as an object of inspection caused by the fact that, the farther the distance from a region to the optical axis of the detection optical system, the lower the MTF (Modulation Transfer Function) for the region, is solved by effectively utilizing the light quantity of a Gaussian light beam emitted by an ordinary low-cost light source, making it possible to detect also a defect caused by typically a very small extraneous material with a size in a range of about 0.1 xcexcm s to about 0.5 xcexcm or even a defect caused by typically a very small extraneous material with a size smaller than 0.1 xcexcm with a high degree of sensitivity and at a high speed.
In addition, according to a configuration described above, an optical image based on a DUV (Deep Ultra Violet) laser beam such as an excima laser obtained from a substrate serving as an object of inspection can be received by a TDI image sensor, making it possible to detect also a defect caused by typically a very small extraneous material with a size in a range of about 0.1 xcexcm to about 0.5 xcexcm or even a defect caused by typically a very small extraneous material with a size smaller than 0.1 xcexcm.
Furthermore, according to a configuration described above, a problem of an insufficient illumination intensity on the periphery of an area of detection on a substrate serving as an object of inspection caused by the fact that, the farther the distance from a region to the optical axis of the detection optical system, the lower the MTF for the region, is solved by effectively utilizing the light quantity of a beam emitted by a lamp serving as a light source, making it possible to detect also a defect caused by typically a very small extraneous material with a size of about 0.1 xcexcm or smaller in the area of detection with a high degree of sensitivity and at a high speed. It should be noted that the detection is moved from one area to another over the substrate serving as an object of inspection.